Facile mineralization and valorization of Cr-containing leather shavings for electrocatalytic H2O2 generation and organic pollutant removal

Today, tens of millions of tons of Cr-containing leather shavings are produced annually, particularly in the developing countries. However, the lack of capitals and appropriate hazard processing technologies often results in the discharge of chromium contaminants, seriously affecting more than one million of population in the world. Herein, we developed a coal-wrapping pyrolysis process to convert hazardous leather shavings into a Cr-N co-doped carbon catalyst. Thanks to the N-rich feature of the leather, excess Cr was fixed into the stable chromium nitride compound which are highly resistant to the oxidation into hazardous high-valence Cr species. This material effectively catalyzed the oxygen reduction reaction to yield H2O2 with selectivity ~ 86% at 0.62 V (vs RHE) thanks to the synergistic effect between N and Cr moieties. Methylene blue, a model organic pollutant in wastewater, can be effectively adsorbed and then decomposed via the in-situ generated hydroxyl radicals. This work provides a green yet practically-feasible way to valorize the Cr-containing leather shavings, and might inspire other scientists to find innovative solutions to address the severe environmental challenges among developing countries.

Automated summary

This study developed a green method to convert Cr-containing leather shavings into carbon catalysts. The carbon catalysts, co-doped with N and Cr, effectively catalyze the oxygen reduction reaction to yield H2O2 with high selectivity. Moreover, these catalysts can adsorb and decompose organic pollutants in wastewater.